1/*
2 * Copyright (c) 2019 Synopsys.
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7/**
8 * @file
9 * @brief Thread context switching
10 *
11 * This module implements the routines necessary for thread context switching
12 * on ARCv2 CPUs.
13 *
14 * See isr_wrapper.S for details.
15 */
16
17#include <zephyr/kernel_structs.h>
18#include <offsets_short.h>
19#include <zephyr/toolchain.h>
20#include <zephyr/linker/sections.h>
21#include <zephyr/arch/cpu.h>
22#include <v2/irq.h>
23#include <swap_macros.h>
24#include <zephyr/arch/arc/asm-compat/assembler.h>
25
26GTEXT(z_arc_switch)
27
28/**
29 *
30 * @brief Initiate a cooperative context switch
31 *
32 * The arch_switch routine is invoked by various kernel services to effect
33 * a cooperative context switch. Prior to invoking arch_switch, the caller
34 * disables interrupts via irq_lock()
35
36 * Given that arch_switch() is called to effect a cooperative context switch,
37 * the caller-saved integer registers are saved on the stack by the function
38 * call preamble to arch_switch. This creates a custom stack frame that will
39 * be popped when returning from arch_switch, but is not suitable for handling
40 * a return from an exception. Thus, the fact that the thread is pending because
41 * of a cooperative call to arch_switch() has to be recorded via the
42 * _CAUSE_COOP code in the relinquish_cause of the thread's k_thread structure.
43 * The _rirq_exit()/_firq_exit() code will take care of doing the right thing
44 * to restore the thread status.
45 *
46 * When arch_switch() is invoked, we know the decision to perform a context
47 * switch or not has already been taken and a context switch must happen.
48 *
49 *
50 * C function prototype:
51 *
52 * void arch_switch(void *switch_to, void **switched_from);
53 *
54 */
55
56SECTION_FUNC(TEXT, z_arc_switch)
57
58	/*
59	 * r0 = new_thread->switch_handle = switch_to thread,
60	 * r1 = &old_thread->switch_handle
61	 * get old_thread from r1
62	 */
63
64	SUBR r2, r1, ___thread_t_switch_handle_OFFSET
65
66	/* _thread_arch.relinquish_cause is 32 bit despite of platform bittnes */
67	_st32_huge_offset _CAUSE_COOP, r2, _thread_offset_to_relinquish_cause, r3
68
69	/*
70	 * Save status32 and blink on the stack before the callee-saved registers.
71	 * This is the same layout as the start of an IRQ stack frame.
72	 */
73	LRR r3, [_ARC_V2_STATUS32]
74	PUSHR r3
75
76#ifdef CONFIG_ARC_HAS_SECURE
77#ifdef CONFIG_ARC_SECURE_FIRMWARE
78	lr r3, [_ARC_V2_SEC_STAT]
79#else
80	mov_s r3, 0
81#endif
82	push_s r3
83#endif
84
85	PUSHR blink
86
87	_store_old_thread_callee_regs
88
89/* disable stack checking here, as sp will be changed to target
90 * thread'sp
91 */
92	_disable_stack_checking r3
93
94	MOVR r2, r0
95
96	_load_new_thread_callee_regs
97
98	breq r3, _CAUSE_RIRQ, _switch_return_from_rirq
99	nop_s
100	breq r3, _CAUSE_FIRQ, _switch_return_from_firq
101	nop_s
102
103	/* fall through to _switch_return_from_coop */
104
105.align 4
106_switch_return_from_coop:
107
108	POPR blink /* pc into blink */
109#ifdef CONFIG_ARC_HAS_SECURE
110	pop_s r3    /* pop SEC_STAT */
111#ifdef CONFIG_ARC_SECURE_FIRMWARE
112	sflag r3
113#endif
114#endif
115	POPR r3    /* status32 into r3 */
116	kflag r3    /* write status32 */
117
118#ifdef CONFIG_INSTRUMENT_THREAD_SWITCHING
119	PUSHR blink
120
121	bl z_thread_mark_switched_in
122
123	POPR blink
124#endif
125	j_s [blink]
126
127
128.align 4
129_switch_return_from_rirq:
130_switch_return_from_firq:
131
132	_set_misc_regs_irq_switch_from_irq
133
134	/* use lowest interrupt priority to simulate
135	 * a interrupt return to load left regs of new
136	 * thread
137	 */
138
139	LRR r3, [_ARC_V2_AUX_IRQ_ACT]
140#ifdef CONFIG_ARC_SECURE_FIRMWARE
141	or r3, r3, (1 << (ARC_N_IRQ_START_LEVEL - 1))
142#else
143	ORR r3, r3, (1 << (CONFIG_NUM_IRQ_PRIO_LEVELS - 1))
144#endif
145
146#ifdef CONFIG_ARC_NORMAL_FIRMWARE
147	mov_s r0, _ARC_V2_AUX_IRQ_ACT
148	mov_s r1, r3
149	mov_s r6, ARC_S_CALL_AUX_WRITE
150	sjli SJLI_CALL_ARC_SECURE
151#else
152	SRR r3, [_ARC_V2_AUX_IRQ_ACT]
153#endif
154#ifdef CONFIG_INSTRUMENT_THREAD_SWITCHING
155	PUSHR blink
156
157	bl z_thread_mark_switched_in
158
159	POPR blink
160#endif
161	rtie
162